Reciprocating intravascular blood pump

ABSTRACT

Apparatus is provided that is configured to be deployed in a lumen of a blood vessel of a subject. The apparatus includes a pump portion, including an anchor configured to engage a wall of the blood vessel in order to maintain the apparatus in place within the blood vessel, and a reciprocating valve coupled to the anchor and including a set of one or more leaflets. A valve driver is configured to drive the reciprocating valve in a reciprocating pattern between (i) a first state in which the leaflets are in an open configuration allowing blood flow through the reciprocating valve, and (ii) a second state in which the leaflets are in a closed configuration inhibiting blood flow through the reciprocating valve. Other embodiments are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. applicationSer. No. 15/831,973, filed Dec. 5, 2017, which is assigned to theassignee of the present application and incorporated herein byreference.

FIELD OF THE INVENTION

Some applications of the invention relate generally to medicalprocedures and implantable devices. More specifically, some applicationsof the invention relate to the use of a mechanical device for deploymentin the circulatory system.

BACKGROUND

Cardiovascular disease is one of the leading causes of death. Bloodpumps for insertion into the vasculature of a patient have beendeveloped to provide mechanical circulatory support by supplementing theblood pumping action of a damaged or diseased heart. An example of anintravascular blood pump is the intra-aortic balloon pump, which is apneumatic device typically deployed in an aorta of a patient to augmentthe pumping action of the heart. Typically, the aortic balloon pumpincludes a balloon, which inflates and deflates in a predeterminedsynchronous pattern with respect to the diastole and systole of thepatient (inflates during diastole and deflates during systole). Theaortic balloon pump typically inflates during diastole, therebyincreasing coronary flow in the coronary arteries, and deflates duringsystole, thereby increasing blood flow forward in the aorta.

SUMMARY OF THE APPLICATION

In accordance with some applications of the present invention, apparatusis provided for deployment in a lumen of a blood vessel of a subject.The apparatus typically affects blood flow in the blood vessel andimproves circulation.

In accordance with some applications of the present invention, theapparatus comprises a reciprocating device, which moves downstream andupstream in the blood vessel in a reciprocating pattern to provide afirst effective surface area when the apparatus moves downstream and asecond effective surface area when the apparatus moves upstream.Typically, when the reciprocating device assumes the first effectivesurface area, blood is pushed downstream in the blood vessel duringdownstream motion of the reciprocating device. Typically, the firsteffective surface area is larger for pushing blood in the blood vesselthan the second effective surface area.

For some applications, the apparatus comprises a pump portion comprisingan anchor and a reciprocating valve. The anchor is configured to engagea wall of the blood vessel in order to maintain the apparatus in placewithin the blood vessel, and the reciprocating valve is coupled to theanchor and comprising a set of one or more leaflets. The apparatusfurther comprises a valve driver configured to drive the reciprocatingvalve in a reciprocating pattern between (i) a first state in which theleaflets are in an open configuration allowing blood flow through thereciprocating valve, and (ii) a second state in which the leaflets arein a closed configuration inhibiting blood flow through thereciprocating valve. During upstream motion of the reciprocating valve,when the leaflets are in the first state, the motion of thereciprocating valve has a relatively small effect on blood flow. Duringdownstream motion of the reciprocating valve, when the leaflets are inthe second state, the motion of the reciprocating valve has asubstantial effect on blood flow, driving blood in a downstreamdirection in the aorta.

In accordance with some applications of the present invention, thereciprocating valve comprises a cylindrical housing to which the set ofone or more leaflets is coupled such that the leaflets in the secondstate inhibit the blood flow through the cylindrical housing. The valvedriver is configured to drive the cylindrical housing to move axiallywith respect to the anchor in the reciprocating pattern.

For some applications, the anchor comprises a generally cylindricalstent, and the pump portion further comprises a blood-proof membranethat is fixed to the stent and to the cylindrical housing so as to (a)inhibit blood flow between the cylindrical housing and the stent and (b)allow axial movement of the cylindrical housing with respect to thestent.

There is therefore provided, in accordance with an Inventive Concept 1of the present invention, apparatus configured to be deployed in a lumenof a blood vessel of a subject, the apparatus including:

a pump portion including:

-   -   an anchor configured to engage a wall of the blood vessel in        order to maintain the apparatus in place within the blood        vessel; and    -   a reciprocating valve coupled to the anchor and including a set        of one or more leaflets; and

a valve driver configured to drive the reciprocating valve in areciprocating pattern between:

-   -   (i) a first state in which the leaflets are in an open        configuration allowing blood flow through the reciprocating        valve, and    -   (ii) a second state in which the leaflets are in a closed        configuration inhibiting blood flow through the reciprocating        valve.

-   Inventive Concept 2. The apparatus according to Inventive Concept 1,    wherein the blood vessel is an aorta of the subject, and wherein the    apparatus is configured to be deployed in the aorta.

-   Inventive Concept 3. The apparatus according to Inventive Concept 1,    wherein the blood vessel is a vena cava of the subject, and wherein    the apparatus is configured to be deployed in the vena cava.

-   Inventive Concept 4. The apparatus according to Inventive Concept 1,    wherein the valve driver includes a rod (a) configured to be    disposed parallel to a longitudinal axis of the blood vessel and    downstream of the reciprocating valve when the apparatus is deployed    in the blood vessel, and (b) configured to push the reciprocating    valve upstream in the blood vessel in the first state, and to pull    the reciprocating valve downstream in the blood vessel in the second    state.

-   Inventive Concept 5. The apparatus according to Inventive Concept 1,    wherein the valve driver is configured to axially move the    reciprocating valve upstream in the first state, and to axially move    the reciprocating valve downstream in the second state.

-   Inventive Concept 6. The apparatus according to Inventive Concept 5,    wherein the valve driver includes a rod (a) disposed parallel to a    longitudinal axis of pump portion 124, and (b) configured to move    the reciprocating valve upstream in the first state and downstream    in the second state.

-   Inventive Concept 7. The apparatus according to Inventive Concept 6,    wherein the rod is (a) disposed downstream of the reciprocating    valve, and (b) configured to push the reciprocating valve upstream    in the first state, and to pull the reciprocating valve downstream    in the second state.

-   Inventive Concept 8. The apparatus according to Inventive Concept 6,    wherein the rod is (a) disposed upstream of the reciprocating valve,    and (b) configured to pull the reciprocating valve upstream in the    first state, and to push the reciprocating valve downstream in the    second state.

-   Inventive Concept 9. The apparatus according to Inventive Concept 1,    wherein the apparatus does not include any leaflets for allowing and    inhibiting blood flow in the blood vessel in addition to the set of    one or more leaflets of the reciprocating valve.

-   Inventive Concept 10. The apparatus according to Inventive Concept    1, wherein the apparatus does not include any leaflets that are    configured to (a) open when the set of one or more leaflets of the    reciprocating valve are in the closed configuration and (b) close    when the set of one or more leaflets of the reciprocating valve are    in the open configuration.

-   Inventive Concept 11. The apparatus according to Inventive Concept    1, wherein the valve driver includes a diametric magnet.

-   Inventive Concept 12. The apparatus according to Inventive Concept    1, wherein the valve driver includes a traverse roll.

-   Inventive Concept 13. The apparatus according to any one of    Inventive Concepts 1-12,

wherein the reciprocating valve includes a cylindrical housing to whichthe set of one or more leaflets is coupled such that the leaflets in thesecond state inhibit the blood flow through the cylindrical housing, and

wherein the valve driver is configured to drive the cylindrical housingto move axially with respect to the anchor in the reciprocating pattern.

-   Inventive Concept 14. The apparatus according to Inventive Concept    13,

wherein the anchor includes a generally cylindrical stent, and

wherein the pump portion further includes a blood-proof membrane that isfixed to the stent and to the cylindrical housing so as to (a) inhibitblood flow between the cylindrical housing and the stent and (b) allowaxial movement of the cylindrical housing with respect to the stent.

-   Inventive Concept 15. The apparatus according to Inventive Concept    14, wherein the blood-proof membrane is fixed to an external surface    of the cylindrical housing.-   Inventive Concept 16. The apparatus according to Inventive Concept    15,

wherein the valve driver is configured to axially move the cylindricalhousing upstream in the first state, and to axially move the cylindricalhousing downstream in the second state, and

wherein the blood-proof membrane is fixed to a downstream portion of theexternal surface of the cylindrical housing and is not fixed to anupstream portion of the external surface of the cylindrical housing, theupstream portion having an axial length, measured along a centrallongitudinal axis of the cylindrical housing, of at least 5 mm.

-   Inventive Concept 17. The apparatus according to Inventive Concept    14, wherein the blood-proof membrane, the cylindrical housing, and    the stent are arranged such that a degree of invagination of the    blood-proof membrane changes during axial movement of the    cylindrical housing with respect to the anchor.-   Inventive Concept 18. The apparatus according to Inventive Concept    17,

wherein the valve driver is configured to axially move the cylindricalhousing upstream in the first state, and to axially move the cylindricalhousing downstream in the second state, and

wherein the blood-proof membrane, the cylindrical housing, and the stentare arranged such that the degree of invagination of the blood-proofmembrane increases during downstream movement of the cylindrical housingand decreases during upstream movement of the cylindrical housing.

-   Inventive Concept 19. The apparatus according to Inventive Concept    17,

wherein the valve driver is configured to axially move the cylindricalhousing upstream in the first state, and to axially move the cylindricalhousing downstream in the second state,

wherein the blood-proof membrane, the cylindrical housing, and the stentare arranged such that the blood-proof membrane is shaped so as todefine an annular chamber between at least a portion of an externalsurface of the cylindrical housing and at least a portion of an innersurface of the generally cylindrical stent, and

wherein the annular chamber has an open downstream end and a closedupstream end defined by a curved portion of the blood-proof membrane.

-   Inventive Concept 20. The apparatus according to Inventive Concept    13,

wherein the valve driver is configured to axially move the cylindricalhousing upstream in the first state, and to axially move the cylindricalhousing downstream in the second state, and

wherein the valve driver is configured to drive the cylindrical housingto move axially between 10 and 20 mm in each of an upstream directionand a downstream direction during an entire cycle of the reciprocatingpattern.

-   Inventive Concept 21. The apparatus according to Inventive Concept    13, wherein the valve driver is configured to axially move the    cylindrical housing downstream in the second state, such that the    reciprocating valve pushes blood at a rate of between 10 and 20 cc    per second.-   Inventive Concept 22. The apparatus according to Inventive Concept    13, wherein the valve driver is configured to axially move the    cylindrical housing downstream in the second state, such that the    reciprocating valve pushes between 10 and 20 cc during an entire    operating cycle of the reciprocating pattern.-   Inventive Concept 23. The apparatus according to any one of    Inventive Concepts 1-12, wherein the valve driver is configured to    drive the valve in the reciprocating pattern at a frequency of 1-5    Hz.-   Inventive Concept 24. The apparatus according to Inventive Concept    23, wherein the valve driver is configured to drive the    reciprocating valve in the reciprocating pattern at a frequency of    2-5 Hz.-   Inventive Concept 25. The apparatus according to any one of    Inventive Concepts 1-12, wherein the valve driver is configured to    drive the valve in the reciprocating pattern at a frequency that is    higher than that of a beating heart.-   Inventive Concept 26. The apparatus according to any one of    Inventive Concepts 1-12, wherein the reciprocating valve has a    thickness of 20-200 microns.-   Inventive Concept 27. The apparatus according to any one of    Inventive Concepts 1-12, wherein the reciprocating valve include a    material selected from the group consisting of: polyurethane or    polyethylene.-   Inventive Concept 28. The apparatus according to any one of    Inventive Concepts 1-12, wherein the set of one or more leaflets    includes 2-6 leaflets.-   Inventive Concept 29. The apparatus according to any one of    Inventive Concepts 1-12, wherein the anchor includes a generally    cylindrical stent.-   Inventive Concept 30. The apparatus according to any one of    Inventive Concepts 1-12, wherein the set of one or more leaflets is    less flexible than the reciprocating valve.-   Inventive Concept 31. The apparatus according to any one of    Inventive Concepts 1-12, wherein the set of one or more leaflets    each have a thickness that is greater than a thickness of the    reciprocating valve.-   Inventive Concept 32. The apparatus according to any one of    Inventive Concepts 1-12,

wherein the set of one or more leaflets are each shaped to define (a) anear side that is coupled to the reciprocating valve and (b) a far side,and

wherein the far side has a thickness that is greater than a thickness ofthe near side.

-   Inventive Concept 33. The apparatus according to any one of    Inventive Concepts 1-12, wherein the anchor includes an O-ring    anchor having an outer diameter of 15-30 mm.-   Inventive Concept 34. The apparatus according to any one of    Inventive Concepts 1-12, wherein the anchor is a first anchor and    wherein the apparatus further includes a second anchor downstream to    the first anchor.-   Inventive Concept 35. The apparatus according to any one of    Inventive Concepts 1-12, wherein the apparatus is not configured to    coordinate the reciprocating pattern with a cardiac cycle of the    subject.-   Inventive Concept 36. The apparatus according to any one of    Inventive Concepts 1-12, wherein the apparatus does not include any    sensor of heart rate or cardiac cycle.-   Inventive Concept 37. The apparatus according to any one of    Inventive Concepts 1-12, wherein the leaflets include a material    selected from the group consisting of: polyurethane or polyethylene.-   Inventive Concept 38. The apparatus according to any one of    Inventive Concepts 1-12, wherein the leaflets include animal tissue.

There is further provided, in accordance with an Inventive Concept 39 ofthe present invention, a method including:

deploying in a lumen of a blood vessel of a subject, in a location thatis downstream of a native aortic valve of a heart of the subject, areciprocating valve including a set of one or more leaflets; and

activating a valve driver to drive the reciprocating valve in areciprocating pattern between:

-   -   (i) a first state in which the leaflets are in an open        configuration allowing blood flow through the reciprocating        valve, and    -   (ii) a second state in which the leaflets are in a closed        configuration inhibiting blood flow through the reciprocating        valve.

-   Inventive Concept 40. The method according to Inventive Concept 39,    wherein deploying the reciprocating valve in the blood vessel    includes deploying the reciprocating valve in a descending aorta.

-   Inventive Concept 41. The method according to Inventive Concept 39,    wherein deploying the reciprocating valve in the blood vessel    includes anchoring the reciprocating valve to the blood vessel using    an anchor configured to engage a wall of the blood vessel.

-   Inventive Concept 42. The method according to Inventive Concept 41,    wherein the anchor includes a generally cylindrical stent.

-   Inventive Concept 43. The method according to Inventive Concept 41,

wherein the reciprocating valve includes a cylindrical housing to whichthe set of one or more leaflets is coupled such that the leaflets in thesecond state inhibit the blood flow through the cylindrical housing, and

wherein activating the valve driver includes activating the valve driverto drive the cylindrical housing to move axially with respect to theanchor in the reciprocating pattern.

-   Inventive Concept 44. The method according to Inventive Concept 43,

wherein deploying the reciprocating valve in the blood vessel includesanchoring the reciprocating valve to the blood vessel using a generallycylindrical stem configured to engage a wall of the blood vessel, and

wherein a blood-proof membrane is fixed to the stent and to an externalsurface of the cylindrical housing so as to (a) inhibit blood flowbetween the cylindrical housing and the stent and (b) allow axialmovement of the cylindrical housing with respect to the stent.

-   Inventive Concept 45. The method according to Inventive Concept 44,    wherein the blood-proof membrane is fixed to an external surface of    the cylindrical housing.-   Inventive Concept 46. The method according to Inventive Concept 45,

wherein activating the valve driver includes activating the valve driverto axially move the cylindrical housing upstream in the first state, andto axially move the cylindrical housing downstream in the second state,and

wherein the blood-proof membrane, the cylindrical housing and the stentare arranged such that a degree of invagination of the blood-proofmembrane increases during downstream movement of the cylindrical housingand decreases during upstream movement of the cylindrical housing.

-   Inventive Concept 47. The method according to Inventive Concept 45,

wherein activating the valve driver includes activating the valve driverto axially move the cylindrical housing upstream in the first state, andto axially move the cylindrical housing downstream in the second state,and

wherein the blood-proof membrane is fixed to a downstream portion of theexternal surface of the cylindrical housing and is not fixed to anupstream portion of the external surface of the cylindrical housing, theupstream portion having an axial length, measured along a centrallongitudinal axis of the cylindrical housing, of at least 5 mm.

-   Inventive Concept 48. The method according to Inventive Concept 44,    wherein the blood-proof membrane, the cylindrical housing, and the    stent are arranged such that a degree of invagination of the    blood-proof membrane changes during axial movement of the    cylindrical housing with respect to the anchor.-   Inventive Concept 49. The method according to Inventive Concept 48,

wherein activating the valve driver includes activating the valve driverto axially move the cylindrical housing upstream in the first state, andto axially move the cylindrical housing downstream in the second state,and

wherein the blood-proof membrane, the cylindrical housing, and the stentare arranged such that the degree of invagination of the blood-proofmembrane increases during downstream movement of the cylindrical housingand decreases during upstream movement of the cylindrical housing.

-   Inventive Concept 50. The method according to Inventive Concept 48,

wherein activating the valve driver includes activating the valve driverto axially move the cylindrical housing upstream in the first state, andto axially move the cylindrical housing downstream in the second state,

wherein the blood-proof membrane, the cylindrical housing, and the stentare arranged such that the blood-proof membrane is shaped so as todefine an annular chamber between at least a portion of an externalsurface of the cylindrical housing and at least a portion of an innersurface of the generally cylindrical stent, and

wherein the annular chamber has an open downstream end and a closedupstream end defined by a curved portion of the blood-proof membrane.

-   Inventive Concept 51. The method according to Inventive Concept 39,    wherein activating the valve driver includes activating the valve    driver to (a) axially move the reciprocating valve upstream in the    blood vessel in the first state, and (b) axially move the    reciprocating valve downstream in the blood vessel in the second    state.-   Inventive Concept 52. The method according to Inventive Concept 51,    wherein activating the valve driver includes activating the valve    driver to drive a rod: (a) to move the reciprocating valve upstream    in the blood vessel in the first state and downstream in the blood    vessel in the second state.-   Inventive Concept 53. The method according to Inventive Concept 52,    wherein activating the valve driver includes activating the valve    driver to drive the rod: (a) to push the reciprocating valve    upstream in the blood vessel in the first state, and (b) to pull the    reciprocating valve downstream in the blood vessel in the second    state.-   Inventive Concept 54. The method according to Inventive Concept 52,    wherein activating the valve driver includes activating the valve    driver to drive the rod: (a) to pull the reciprocating valve    upstream in the blood vessel in the first state, and (b) to push the    reciprocating valve downstream in the blood vessel in the second    state.-   Inventive Concept 55. The method according to Inventive Concept 39,    wherein the method further includes not deploying any leaflets for    allowing and inhibiting blood flow in the blood vessel in addition    to the set of one or more leaflets of the reciprocating valve.-   Inventive Concept 56. The method according to Inventive Concept 39,    wherein activating the valve driver includes activating the valve    driver to drive a rod: (a) to push the reciprocating valve upstream    in the blood vessel in the first state, and (b) to pull the    reciprocating valve downstream in the blood vessel in the second    state.-   Inventive Concept 57. The method according to Inventive Concept 56,    wherein activating the valve driver to drive the rod includes    activating the valve driver to drive the rod using a traverse roll    mechanism.-   Inventive Concept 58. The method according to Inventive Concept 39,    wherein activating the valve driver does not include activating the    valve driver to coordinate the reciprocating pattern with a cardiac    cycle of the subject.-   Inventive Concept 59. The method according to Inventive Concept 39,    wherein the method does not include internally or externally    coupling to the subject any sensor of heart rate or cardiac cycle.

There is further provided, in accordance with an Inventive Concept 60 ofthe present invention, apparatus configured to be deployed in a lumen ofa blood vessel of a subject, the apparatus including:

a reciprocating device configured to move downstream and upstream in theblood vessel in a reciprocating pattern to provide:

-   -   a first effective surface area of the device for pushing blood        downstream in the blood vessel during downstream motion of the        reciprocating device, and    -   a second effective surface area of the device during upstream        motion of the reciprocating device, the first effective surface        area being larger for pushing blood in the blood vessel than the        second effective surface area; and

a device driver configured to drive the reciprocating device in thereciprocating pattern.

-   Inventive Concept 61. The apparatus according to Inventive Concept    60, wherein the reciprocating device includes a flexible membrane.

The present invention will be more fully understood from the followingdetailed description of applications thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration of apparatus for deployment in alumen of a blood vessel of a subject being deployed in the lumen, inaccordance with some applications of the present invention;

FIGS. 1B and 1C are schematic illustrations of the apparatus beingoperated in the lumen of the blood vessel in a first state in whichblood is allowed to flow through the apparatus (FIG. 1B), and a secondstate in which blood is inhibited from flowing through the apparatus(FIG. 1C), in accordance with some applications of the presentinvention;

FIGS. 2A and 2B are schematic illustrations of additional views of theapparatus in the first and second states, in accordance with someapplications of the present invention;

FIGS. 3A and 3B are schematic illustrations of a top view of theapparatus in the first and second states, in accordance with someapplications of the present invention;

FIGS. 4A and 4B are schematic illustrations of the apparatus in thefirst and second states, and coupled to a power source for powering theapparatus, in accordance with some applications of the presentinvention;

FIGS. 5A and 5B are schematic illustrations of cross sections of theapparatus in the first and second states, and a power source forpowering the apparatus, in accordance with some applications of thepresent invention;

FIGS. 6A, 6B, and 6C are schematic illustrations of a reciprocatingvalve, in accordance with some applications of the present invention;

FIG. 7 is a schematic illustration of leaflets of the apparatus, inaccordance with some applications of the present invention;

FIGS. 8A and 8B are schematic illustrations of another apparatus fordeployment in a lumen of blood vessel of a subject, in accordance withsome applications of the present invention;

FIGS. 9A-B are schematic side and cross-sectional views, respectively,of the apparatus of FIGS. 8A and 8B in a second state in which leafletsare in a closed configuration, in accordance with some applications ofthe present invention;

FIGS. 10A-B are schematic side and cross-sectional views, respectively,of the apparatus of FIGS. 8A and 8B in a first state in which leafletsare in an open configuration, in accordance with some applications ofthe present invention;

FIG. 11 is a schematic illustration of the apparatus of FIGS. 8A and 8Bdeployed in the lumen of the blood vessel, in accordance with someapplications of the present invention; and

FIG. 12 is a schematic illustration of representative phases of thereciprocating pattern of the apparatus of FIGS. 8A and 8B during asingle of cycle of the reciprocating pattern, in accordance with someapplications of the present invention.

DETAILED DESCRIPTION OF APPLICATIONS

Reference is first made to FIGS. 1A-C, which are schematic illustrationsof apparatus 20 advanced and subsequently deployed in a lumen of a bloodvessel 90 of a subject, in accordance with some applications of thepresent invention. Typically, apparatus 20 is advanced in the lumen ofblood vessel 90 in a minimally-invasive procedure. Apparatus 20 is thendeployed in a desired location in the blood vessel to facilitate bloodflow in the blood vessel, as described hereinbelow. For example,apparatus 20 may be advanced in a delivery tool, e.g., a catheter 92,through a femoral artery in a retrograde direction and along the aortauntil a desired location downstream of a native aortic valve is reached.Apparatus 20 is then deployed in the desired location in the aorta toimprove blood flow in the aorta. As shown in FIG. 1A, apparatus 20 isadvanced in a retrograde direction in the aorta in a collapsedconfiguration. Upon reaching the desired location in the aorta (e.g., inthe descending aorta), apparatus 20 begins operation, as illustrated inFIGS. 1B-C. (Typically, apparatus 20 is not implanted too close to theaortic valve, such that the blood pressure stored in the aortic wallbetween the aortic valve and apparatus 20 during systole is sufficientto provide blood flow to the coronary arteries during diastole.)

As shown in FIGS. 1B-C, for some applications, apparatus 20 comprises apump portion 24 comprising an anchor 30 which engages a wall of bloodvessel 90 in order to maintain apparatus 20 in place within blood vessel90. Anchor 30 typically comprises an O-ring anchor having an outerdiameter D1 of 15-30 mm, e.g., 20-30 mm.

Pump portion 24 further comprises a reciprocating device, e.g.,reciprocating valve 34, coupled to anchor 30 and comprising (e.g.,shaped to define) a set of one or more leaflets 40, e.g., 2-6 leaflets40. It is noted that for some applications, leaflets 40 are not shown toscale and may be larger in size than as shown in FIGS. 1B-C. Whenleaflets 40 are in an open configuration (for example as shown in FIG.1B), reciprocating valve 34 is shaped to define one or more windows 42in place of where leaflets 40 are positioned in reciprocating valve 34when leaflets 40 are in a closed configuration (for example as shown inFIG. 1C). It is noted that for some applications, windows 42 are notshown to scale and may be larger in size than as shown in the figures.

Typically, reciprocating valve 34 is a thin and flexible valve (e.g., amembrane) having a thickness T1 of 20-200 microns, e.g., 100-200microns. Reciprocating valve 34 typically comprises a flexible materialfacilitating the reciprocating motion of reciprocating valve 34, and dueto its thinness, minimizing development of tension and compression inthe flexible material during motion of reciprocating valve 34. Forexample, reciprocating valve 34 may comprise a biocompatible syntheticmaterial, e.g., polyurethane or polyethylene. For other applications,reciprocating valve 34 comprises a flexible, thin animal tissue.

For some applications, reciprocating valve 34 may be similar to a knowncommercial valve, such as the Edwards Sapien™ valve, mutatis mutandis.

In contrast, leaflets 40 are typically less flexible than reciprocatingvalve 34, and have a thickness that is greater than the thickness ofreciprocating valve 34. Leaflets 40 are typically thicker and lessflexible than reciprocating valve 34 in order to allow leaflets 40 totransition properly between open and closed configurations as describedhereinbelow, and maintain a suitable seal with windows 42 ofreciprocating valve 34. For some applications, leaflets 40 compriseanimal tissue, e.g., porcine pericardium, which is typically arelatively thick membrane (e.g., on the order of 1-2 mm). Alternatively,leaflets 40 comprise a biocompatible synthetic material such aspolyurethane or polyethylene.

Apparatus 20 further comprises a valve driver 50 configured to drivereciprocating valve 34 in a reciprocating pattern between a first state,shown in FIGS. 1B and 2A, in which leaflets 40 are in an openconfiguration, and a second state shown in FIGS. 1C and 2B, in whichleaflets 40 are in a closed configuration. Typically, valve driver 50comprises a motor 51, which is shown highly schematically in FIGS. 2Aand 2B. For example, motor 51 may comprise a linear motor. For example,a housing 53 in which the motor is disposed may be coated, e.g., withpolytetrafluoroethylene (PTFE).

Typically, in the first state when leaflets 40 are in an openconfiguration, blood is allowed to flow through reciprocating valve 34.In the second state, when leaflets 40 are in the closed configuration,blood is typically inhibited from flowing through reciprocating valve34. Valve driver 50 is typically configured to move (e.g., push)reciprocating valve 34 upstream in blood vessel 90 in the first state(shown in FIG. 1B), causing opening of leaflets 40 and allowing bloodflow through reciprocating valve 34 in a downstream direction in bloodvessel 90. Valve driver 50 is typically configured to move (e.g., pull)reciprocating valve 34 downstream in blood vessel 90 in the second state(shown in FIG. 1C), causing closing of leaflets 40 and inhibiting bloodflow through reciprocating valve 34 in a downstream direction in bloodvessel 90. In the transition between the first state (FIG. 1B) and thesecond state (FIG. 1C), the motion of reciprocating valve 34 being moved(e.g., pulled) downstream by reciprocating valve driver 50 pushes blooddownstream in blood vessel 90, thereby affecting blood flow in bloodvessel 90.

Typically, in the second state in which reciprocating valve 34 is moved(e.g., pulled) downstream and leaflets 40 are in the closedconfiguration, reciprocating valve 34 assumes a first effective surfacearea of reciprocating valve 34 for pushing blood downstream in bloodvessel 90, due to the orientation of the leaflets. In the first state inwhich reciprocating valve 34 is moved (e.g., pushed) upstream andleaflets 40 are in the open configuration, reciprocating valve 34assumes a second effective surface area of reciprocating valve 34(having a relatively small effect on blood flow). The first effectivesurface area is typically larger than the second effective surface area,and has a substantial effect on blood flow, driving blood in adownstream direction in the aorta by pushing the blood.

For some applications, valve driver 50 comprises a rod 26 configured tobe disposed parallel to a longitudinal axis of the blood vessel (and,typically, to a longitudinal axis of pump portion 24) and downstream ofreciprocating valve 34 when apparatus 20 is deployed in blood vessel 90.Rod 26 moves (e.g., pushes) reciprocating valve 34 upstream in the bloodvessel in the first state, and moves (e.g., pulls) reciprocating valve34 downstream in blood vessel 90 in the second state. Typically, but notnecessarily, reciprocating valve 34 assumes a convex configuration (asviewed from upstream of reciprocating valve 34) when rod 26 moves (e.g.,pushes) reciprocating valve 34 upstream in blood vessel 90 in the firststate, and a concave configuration when rod 26 moves (e.g., pulls)reciprocating valve 34 downstream in blood vessel 90 in the secondstate. Alternatively, rod 26 is disposed upstream of reciprocating valve34, and rod 26 pulls reciprocating valve 34 upstream in the blood vesselin the first state, and pushes reciprocating valve 34 downstream inblood vessel 90 in the second state (configuration not shown).

Reciprocating valve 34 typically affects blood flow in blood vessel 90by reciprocation between the first state in which rod 26 moves (e.g.,pushes) reciprocating valve 34 upstream and leaflets 40 are in the openconfiguration, and the second state, in which rod 26 moves (e.g., pulls)reciprocating valve 34 downstream and the leaflets are in the closedconfiguration. The reciprocating motion of reciprocating valve 34typically pushes the blood downstream in blood vessel 90, therebyassisting functioning of the heart. For example, apparatus 20 may bedeployed in an aorta of the subject in a location that is downstream ofa native aortic valve of the subject, e.g., in a descending aorta of thesubject (although it is noted that apparatus 20 may be deployed in theaorta in a location that is closer to the native aortic valve, orelsewhere in the circulatory system). Operating apparatus 20 in theaorta typically increases blood flow in the aorta and reduces pressurein the ascending aorta (upstream of reciprocating valve 34).

Apparatus 20 typically comprises control circuitry 60 that is configuredto control the reciprocating motion of reciprocating valve 34.Typically, apparatus 20 is not operated in coordination with a cardiaccycle of the subject. Typically, apparatus 20 is not configured tocoordinate the reciprocating pattern with a cardiac cycle of thesubject. Thus, apparatus 20 typically does not comprise any heart rateor cardiac cycle sensor (such as an electrode for sensing the heart rateor the cardiac cycle). For example, the reciprocating motion ofreciprocating valve 34 (moving (e.g., pushing) of reciprocating valve 34upstream and moving (e.g., pulling of reciprocating valve 34 downstream)is typically not dependent on the frequency of heart beats, andreciprocating valve 34 is typically not operated in a synchronouspattern with respect to the diastole and systole of the subject.Typically, apparatus 20 is operated such that the reciprocating motionof reciprocating valve 34 is at a frequency that is higher than that ofa beating heart. For example, apparatus 20 operates at a reciprocatingfrequency of 1-5 Hz, e.g., 2-5 Hz. For some applications, apparatus 20is configured to operate at a reciprocating frequency that is adjustableonly by an external user interface.

It is noted that FIGS. 1A-C show blood vessel 90 as the aorta andapparatus 20 is shown in the aorta by way of illustration and notlimitation. For some applications, apparatus 20 is deployed in anotherblood vessel 90, e.g., a vena cava of the subject.

Reference is now made to FIGS. 2A-B, which are schematic illustrationsof additional views of apparatus 20, in accordance with someapplications of the present invention. FIG. 2A shows a side view ofapparatus 20 in the first state in which leaflets 40 are in the openconfiguration, and FIG. 2B shows a side view of apparatus 20 in thesecond state in which leaflets 40 are in the closed configuration.

It is noted that apparatus 20 typically does not comprise any leafletsthat are configured to (a) open when the set of one or more leaflets 40of reciprocating valve 34 are in the closed configuration and (b) closewhen the set of one or more leaflets 40 of reciprocating valve 34 are inthe open configuration. Indeed, apparatus 20 typically does not compriseany leaflets for allowing and inhibiting blood flow in the blood vessel,in addition to the set of one or more leaflets 40 of reciprocating valve34.

For some applications, apparatus 20 comprises a second anchor 31positioned downstream of anchor 30 and configured to engage the wall ofblood vessel 90 to anchor apparatus 20 to the wall of blood vessel 90.For some applications, second anchor 31 comprises a plurality of ribs32, e.g., 2-6 ribs 32.

For some applications, apparatus 20 additionally comprises a pluralityof self-expandable support members 38 extending from a base portion 80of apparatus 20 to anchor 30. Support members 38 are typically shaped sothat apparatus 20 is retrievable. For some applications, support members38 are arranged in the form of a stent (and not as shown in thefigures).

Reference is now made to FIGS. 3A-B, which are top views of apparatus20, in accordance with some applications of the present invention. FIG.3A shows a top view of apparatus 20 in the first state with leaflets 40in the open configuration and wrapped around rod 26, allowing blood flowthrough reciprocating valve 34. FIG. 3B shows a top view of apparatus 20in the second state in which leaflets 40 are in the closed configurationand blood is inhibited from flowing through reciprocating valve 34.

Reference is now made to FIGS. 4A-B, which are schematic illustrationsof apparatus 20 in the first state (FIG. 4A) and in the second state(FIG. 4B). FIGS. 4A-B additionally show a power source for poweringvalve driver 50, for driving reciprocating valve 34. For someapplications, apparatus 20 is powered by a radiofrequency (RF)-basedsystem illustrated in FIGS. 4A-B. For such applications, at least onetransmitter coil 96 is disposed outside the subject's body, and at leastone receiver coil 98 is implanted in the subject. Transmitter coil 96typically generates power of 3 kHz-14 MHz, e.g., 6-8 MHz or 13-14 MHz.

As shown in FIGS. 4A-B, external RF transmitter coil 96 is coupled tothe subject (e.g., by a chest-band 94). RF transmitter coil 96 inducescurrent in RF receiver coil 98 which is typically implantedsubcutaneously in the subject. Power is typically carried through a wire99 from receiver coil 98 to motor 51 of valve driver 50 (shownschematically in FIGS. 2A and 2B) in apparatus 20. Valve driver 50 inturn drives rod 26 in an upstream and downstream direction to move(e.g., push and pull) reciprocating valve 34 upstream and downstream inthe blood vessel.

For some applications, valve driver 50 comprises control circuitry 60(such as shown highly schematically in FIGS. 2A-B). For otherapplications, an external unit is provided that comprises controlcircuitry 60, which is electrically coupled to transmitter coil 96 (suchas shown highly schematically in FIGS. 4A-B); in this configuration,control circuitry 60 controls the operation of valve driver 50 via theparameters of the power transmitted to receiver coil 98.

Reference is now made to FIGS. 5A-B, which are cross sections ofapparatus 20, in accordance with some applications of the presentinvention. FIG. 5A shows a cross section of apparatus 20 in the firststate with leaflets 40 in the open configuration and wrapped around rod26, allowing blood flow through reciprocating valve 34. FIG. 5B shows across section of apparatus 20 in the second state in which leaflets 40are in the closed configuration and blood is inhibited from flowingthrough reciprocating valve 34.

For some applications, valve driver 50 comprises a diametric magnet 55,which causes rotation of longitudinal element 36 which drives rod 26 inan upstream and downstream direction in blood vessel 90. For someapplications, rod 26 is reciprocally driven by a traverse roll mechanism46 operating between longitudinal element 36 and rod 26. Additionally,or alternatively, an extracorporeal rotating magnet 510 drivesintracorporeal diametric magnet 55 to rotate, thus rotating longitudinalelement 36 and driving rod 26 upstream and downstream in blood vessel90.

Reference is now made to FIGS. 1A-C, 2A-B, 3A-B and 5A-B. Anchor 30 isshown in the drawings as a ring anchor (e.g., an O-ring) by way ofillustration and not limitation. For some applications, apparatus 20 ismaintained in place in blood vessel 90 by an alternative type of anchor.For example, apparatus 20 may be anchored to a wall of blood vessel 90by a soft porous material, e.g., a suitable gauze, which at firstabsorbs blood but over time becomes less soft and generally impermeableto blood due to clotting of the blood therein.

Reference is now made to FIGS. 6A-C, which are schematic illustrationsof reciprocating valve 34 in accordance with some applications of thepresent invention. Typically, reciprocating valve 34 is clamped betweentwo toroidal plates, e.g., washers 500, such that the edge along theperimeter of reciprocating valve 34 is compressed between washers 500.Typically, washers 500 comprise silicone, or another suitable, resilientmaterial (which is typically slightly flexible, but may alternatively berigid). Clamping reciprocating valve 34 between washers 500 typicallysecures reciprocating valve 34 and facilitates anchoring ofreciprocating valve 34 to anchor 30. As shown in the cross section inFIG. 6C, each washer 500 is shaped to define a rounded inner edge 501 inorder to reduce any damage to reciprocating valve 34 during thereciprocating motion of reciprocating valve 34. (Leaflets 40 and windows42 are not shown in FIGS. 6A-C.)

Reference is now made to FIG. 7, which is a schematic illustration ofleaflets 40 in accordance with some applications of the presentinvention. As described hereinabove with reference to FIGS. 1B-C, theoverall thickness of leaflets 40 is greater than that of reciprocatingvalve 34. Additionally, for some applications, the thickness of leaflet40 in a near side of the leaflet (the near side being the side that iscoupled to reciprocating valve 34) is less than a thickness of theleaflet at a far side of the leaflet (the far side being the side of theleaflet that is farther away from the coupling point of the leaflet withreciprocating valve 34). Typically, the thickness of leaflet 40increases as it extends away from the coupling point betweenreciprocating valve 34 and leaflet 40. As shown in FIG. 7, leaflet 40has a first thickness T2 at, or near, the coupling point withreciprocating valve 34. As leaflet 40 extends away from the couplingpoint with reciprocating valve 34, the thickness thereof increasesgradually to a thickness T3. Leaflet 40 is typically thinner at thecoupling point with reciprocating valve 34 in order to provide theleaflet with greater flexibility at the coupling point, to allow foreasy motion of leaflets 40 at the coupling point. The increasedthickness T3 of leaflets 40 facilitates proper placement of leaflets 40against windows 42.

Reference is now made to FIGS. 8A and 8B, which are schematicillustrations of apparatus 120 for deployment in a lumen of blood vessel90 of a subject, in accordance with some applications of the presentinvention. FIG. 8A shows apparatus 120 fully assembled, and FIG. 8Bshows an exploded view of the elements of apparatus 120. Other than asdescribed hereinbelow, apparatus 120 is generally similar to apparatus20, described hereinabove with reference to FIGS. 1A-7, and mayimplement any of the techniques thereof, including deploymenttechniques, mutatis mutandis, and like reference numerals refer to likeelements.

Reference is further made to FIGS. 9A-B, which are schematic side andcross-sectional views, respectively, of apparatus 120 in the secondstate in which leaflets 140 are in the closed configuration, inaccordance with some applications of the present invention. Reference isstill further made to FIGS. 10A-B, which are schematic side andcross-sectional views, respectively, of apparatus 120 in the first statein which leaflets 140 are in the open configuration, in accordance withsome applications of the present invention.

Apparatus 120 comprises a pump portion 124 comprising an anchor 130which engages a wall of blood vessel 90 in order to maintain apparatus120 in place within blood vessel 90. For some applications, anchor 130comprises a generally cylindrical stent 132. For example, stent 132 mayhave an outer diameter D1 of 15-30 mm, e.g., 20-30 mm.

Pump portion 124 further comprises a reciprocating valve 134, coupled toanchor 130 and comprising (e.g., shaped to define) a set of one or moreleaflets 140, e.g., 2-6 leaflets 140. For some applications,reciprocating valve 134 may be similar to a known commercial valve, suchas the Edwards Sapien™ valve, mutatis mutandis.

Apparatus 120 further comprises a valve driver 150 configured to drivereciprocating valve 134 in a reciprocating pattern between a firststate, shown in FIGS. 10A-B, in which leaflets 140 are in an openconfiguration, and a second state shown in FIGS. 8A-B and 9A-B, in whichleaflets 140 are in a closed configuration. Typically, in the firststate when leaflets 140 are in an open configuration, blood is allowedto flow through reciprocating valve 134. In the second state, whenleaflets 140 are in the closed configuration, blood is typicallyinhibited from flowing through reciprocating valve 134.

Valve driver 150 may implement any of the techniques of valve driver 50described hereinabove. For example, for some applications, valve driver150 comprises control circuitry 60 (such as shown highly schematicallyin FIGS. 9B and 10B). For other applications, an external unit isprovided that comprises control circuitry 60. Control circuitry 60 isdescribed hereinabove.

For some applications, valve driver 150 comprises a rod 126 configuredto be disposed parallel to a longitudinal axis of the blood vessel (and,typically, to a longitudinal axis of pump portion 124) and downstream ofreciprocating valve 134 when apparatus 120 is deployed in blood vessel90. Rod 126 moves (e.g., pushes) reciprocating valve 134 upstream in theblood vessel in the first state, and moves (e.g., pulls) reciprocatingvalve 134 downstream in blood vessel 90 in the second state.Alternatively, rod 126 is disposed upstream of reciprocating valve 134,and rod 126 pulls reciprocating valve 134 upstream in the blood vesselin the first state, and pushes reciprocating valve 134 downstream inblood vessel 90 in the second state (configuration not shown).

As described in more detail hereinbelow with reference to FIG. 12,reciprocating valve 134 typically affects blood flow in blood vessel 90by reciprocation between the first state in which rod 126 moves (e.g.,pushes) reciprocating valve 134 upstream and leaflets 140 are in theopen configuration, and the second state, in which rod 126 moves (e.g.,pulls) reciprocating valve 134 downstream and the leaflets are in theclosed configuration.

Typically, reciprocating valve 134 comprises a cylindrical housing 144to which the set of one or more leaflets 140 is coupled such thatleaflets 140 in the second state inhibit the blood flow throughcylindrical housing 144. For example, leaflets 140 may be coupled to aninternal surface of cylindrical housing 144. Cylindrical housing 144 maybe elliptical (e.g., circular, as shown), or may have another shape.Valve driver 150 is configured to drive cylindrical housing 144 to moveaxially with respect to anchor 130 in the reciprocating pattern.

For some applications, pump portion 124 further comprises a blood-proofmembrane 148 that is fixed to stent 132 and to cylindrical housing 144so as to (a) inhibit blood flow between cylindrical housing 144 andstent 132 and (b) allow axial movement of cylindrical housing 144 withrespect to stent 132. Blood-proof membrane 148 may be fixed to anexternal surface 152 of cylindrical housing 144 (as shown), an internalsurface of cylindrical housing 144, and/or an end surface of cylindricalhousing 144.

Optionally, blood-proof membrane 148 comprises a polymer (such aspolyurethane), latex, silicone, or a fabric.

For some applications, elements of apparatus 120 have one or more of thefollowing dimensions:

-   -   cylindrical housing 144—an axial length of between 10 and 25 mm,        such as between 12 and 20 mm, e.g., 15 mm,    -   cylindrical housing 144—an outer diameter of between 10 and 25        mm, such as between 12 and 20 mm, e.g., 15 mm,    -   rod 126—an outer diameter of between 10 and 25 mm, such as        between 12 and 20 mm, e.g., 15 mm,    -   housing 53—an outer diameter of between 4 and 10 mm, such as        between 5 and 8 mm, e.g., 7 mm,    -   housing 53—an axial length of between 10 and 30 mm, such as        between 15 and 25 mm, e.g., 20 mm,    -   stent 132—an outer diameter of between 15 and 25 mm, such as 20        mm, and/or    -   stent 132—an axial length of between 25 and 50 mm, such as        between 30 and 40 mm.

For some applications, as labeled in FIGS. 9B and 10B, blood-proofmembrane 148 is fixed to external surface 152 of cylindrical housing144. As mentioned above, for some applications valve driver 150 isconfigured to axially move cylindrical housing 144 upstream in the firststate, and to axially move cylindrical housing 144 downstream in thesecond state; in some of these applications, blood-proof membrane 148 isfixed to a downstream portion 154A of external surface 152 ofcylindrical housing 144 and is not fixed to an upstream portion 154B ofexternal surface 152 of cylindrical housing 144. For example, upstreamportion 154E may have an axial length L, measured along a centrallongitudinal axis 156 of cylindrical housing 144, of at least 3 mm, suchas at least 5 mm, e.g., at least 10 mm. Optionally, downstream portion154A reaches a downstream end of cylindrical housing 144; furtheroptionally, downstream portion 154A is essentially only near thedownstream end of cylindrical housing 144, e.g., extends less than 1 mmupstream from the downstream end of cylindrical housing 144. Optionally,blood-proof membrane 148 is fixed to downstream portion 154A bystitching, welding, gluing, and/or squeezing (e.g., using a ring).

Similarly, blood-proof membrane 148 is fixed to an axial portion ofanchor 130, e.g., stent 132, optionally using any of the techniquesdescribed in the immediately preceding paragraph.

For some applications, an axial length of a portion of blood-proofmembrane 148 that touches upstream portion 154B of external surface 152of cylindrical housing 144 varies based on the degree of invagination ofblood-proof membrane 148 (i.e., how much the membrane is folded overinto itself), which typically changes during axial movement ofcylindrical housing 144 with respect to anchor 130, as describedhereinbelow with reference to FIG. 12. (Thus, a portion of blood-proofmembrane 148, even though it is not fixed to upstream portion 154B, maynevertheless sometimes touch upstream portion 154B, such as shown, forexample, in FIG. 10B and other figures; the level of touching variesbased on the level of invagination.)

As mentioned above, for some applications valve driver 150 is configuredto axially move cylindrical housing 144 upstream in the first state, andto axially move cylindrical housing 144 downstream in the second state;in some of these applications, blood-proof membrane 148, cylindricalhousing 144, and stent 132 are arranged such that blood-proof membrane148 is shaped so as to define an annular chamber 158 between at least aportion of external surface 152 of cylindrical housing 144 and at leasta portion of an inner surface 162 of generally cylindrical stem 132. (Itis noted that an axial length of annular chamber 158 varies based on thedegree of invagination of blood-proof membrane 148 (i.e., how much themembrane is folded over into itself), which typically changes duringaxial movement of cylindrical housing 144 with respect to anchor 130, asdescribed hereinbelow with reference to FIG. 12.)

Typically, annular chamber 158 has an open downstream end 164 and aclosed upstream end 166 defined by a curved portion 168 of blood-proofmembrane 148. Typically, because annular chamber 158 has closed upstreamend 166, valve driver 150 requires less power to move cylindricalhousing 144 upstream that would be necessary if annular chamber 158 hadan open upstream end.

Alternatively, blood-proof membrane 148 is arranged in an oppositedirection from that shown in the figures, such that annular chamber 158has a closed downstream end and an open upstream end defined by curvedportion 168 of blood-proof membrane 148.

Reference is now made to FIG. 11, which is a schematic illustration ofapparatus 120 deployed in the lumen of blood vessel 90, in accordancewith some applications of the present invention. Apparatus 120 mayoptionally implement the power transmission techniques describedhereinabove for apparatus 20 with reference to FIGS. 4A-B. Thereciprocating motion of reciprocating valve 134 typically pushes theblood downstream in blood vessel 90, thereby assisting functioning ofthe heart. For example, apparatus 120 may be deployed in an aorta of thesubject in a location that is downstream of a native aortic valve of thesubject, e.g., in a descending aorta of the subject (although it isnoted that apparatus 120 may be deployed in the aorta in a location thatis closer to the native aortic valve, or elsewhere in the circulatorysystem). Operating apparatus 120 in the aorta typically increases bloodflow in the aorta and reduces pressure in the ascending aorta (upstreamof reciprocating valve 134).

Reference is now made to FIG. 12, which is a schematic illustration ofrepresentative phases of the reciprocating pattern of apparatus 120during a single of cycle of the reciprocating pattern, in accordancewith some applications of the present invention.

The upper row of FIG. 12 shows apparatus 120 when reciprocating valve134 is in the second state, in which leaflets 140 are in the closedconfiguration, such that blood is inhibited from flowing throughreciprocating valve 134. In Stage A of the cycle of the reciprocatingpattern, compression begins as valve driver 150 moves (e.g., pulls)reciprocating valve 134 downstream in blood vessel 90. Downstreammovement of reciprocating valve 134 from Stage A to Stage D of the cycleof the reciprocating pattern pushes blood downstream in blood vessel 90.For some applications, this downstream movement of reciprocating valve134 pushes blood at a rate of between 10 and 20 cc per second, such asbetween 15 and 20 cc per second, e.g., about 16 cc per second.Alternatively or additionally, for some applications, this downstreammovement of reciprocating valve 134 pushes between 10 and 20 cc, such asbetween 15 and 20 cc, e.g., about 16 cc, during an entire operatingcycle of the reciprocating pattern.

The lower row of FIG. 12 shows apparatus 120 when reciprocating valve134 is in the first state, in which leaflets 140 are in the openconfiguration, such that blood is allowed to flow through reciprocatingvalve 134. As valve driver 150 begins to move (e.g., push) reciprocatingvalve 134 upstream in blood vessel 90 in Stage E of the cycle of thereciprocating pattern, leaflets 140 open (because of the pressuregradient across leaflets 140 created by the upstream motion ofreciprocating valve 134), thereby allowing natural cardiac-drivendownstream blood flow (e.g., during systole) through reciprocating valve134 as reciprocating valve 134 moves upstream from Stage E to Stage H ofthe cycle of the reciprocating pattern.

It is noted that the blood flow symbolically shown in the bottom row ofFIG. 12 is not caused by reciprocating valve 134; when leaflets 140 areopen, reciprocating valve 134 at most interferes only minimally withnatural blood flow. The lengths of the blood-flow arrows in FIG. 12highly symbolically illustrate different flow rates; the relativelengths of the arrows should not be interpreted as representing anyparticular ratios of blood flow rates. In addition, as mentioned above,the reciprocating valves described herein are typically not operated ina synchronous pattern with respect to the diastole and systole of thesubject. Therefore, when Stage E to Stage H of the cycle of thereciprocating pattern happen to fall at least partially during diastole,there may be no or very little blood flow during a portion of the cycleof the reciprocating pattern that happens to fall during diastole.

Upon completion of Stage H of the cycle of the reciprocating pattern,the cycle repeats as valve driver 150 begins to again move (e.g., pull)reciprocating valve 134 downstream in blood vessel 90 at Stage A of thecycle of the reciprocating pattern. As valve driver 150 begins to move(e.g., pull) reciprocating valve 134 downstream in blood vessel 90,leaflets 140 close (because of the pressure gradient across leaflets 140created by the downstream motion of reciprocating valve 134). As aresult, reciprocating valve 134 transitions back to the second statedescribed hereinabove with reference to the upper row of FIG. 12.

For some applications, valve driver 150 is configured to axially movereciprocating valve 134 (and cylindrical housing 144) between 10 and 20mm in each direction (downstream and upstream) during an entire cycle ofthe reciprocating pattern, such as between 12 and 18 mm, e.g., 15 mm.

For some applications, blood-proof membrane 148, cylindrical housing144, and stent 132 are arranged such that a degree of invagination ofblood-proof membrane 148 (i.e., how much the membrane is folded overinto itself) changes during axial movement of cylindrical housing 144with respect to anchor 130. As mentioned above, for some applicationsvalve driver 150 is configured to axially move cylindrical housing 144upstream in the first state, and to axially move cylindrical housing 144downstream in the second state; in some of these applications,blood-proof membrane 148, cylindrical housing 144, and stent 132 arearranged such that the degree of invagination of blood-proof membrane148 increases during downstream movement of cylindrical housing 144 (asshown in the upper row of FIG. 12) and decreases during upstreammovement of cylindrical housing 144 (as shown in the lower row of FIG.12).

For some applications, apparatus 120 is configured such that allimplanted elements of apparatus 120 other than anchor 130 (e.g., stentl32) may be decoupled from anchor 130 after implantation and explanted,leaving anchor 130 implanted. Optionally, these explanted elements maybe replaced with other similar elements by introducing these othersimilar elements into the body and coupling them to anchor 130.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

1. Apparatus configured to be deployed in a lumen of a blood vessel of asubject, the apparatus comprising: a pump portion comprising: an anchorconfigured to engage a wall of the blood vessel in order to maintain theapparatus in place within the blood vessel; and a reciprocating valvecoupled to the anchor and comprising a set of one or more leaflets; anda valve driver configured to drive the reciprocating valve in areciprocating pattern between: (i) a first state in which the leafletsare in an open configuration allowing blood flow through thereciprocating valve, and (ii) a second state in which the leaflets arein a closed configuration inhibiting blood flow through thereciprocating valve.
 2. The apparatus according to claim 1, wherein theblood vessel is an aorta of the subject, and wherein the apparatus isconfigured to be deployed in the aorta.
 3. The apparatus according toclaim 1, wherein the valve driver comprises a rod (a) configured to bedisposed parallel to a longitudinal axis of the blood vessel anddownstream of the reciprocating valve when the apparatus is deployed inthe blood vessel, and (b) configured to push the reciprocating valveupstream in the blood vessel in the first state, and to pull thereciprocating valve downstream in the blood vessel in the second state.4. The apparatus according to claim 1, wherein the valve driver isconfigured to axially move the reciprocating valve upstream in the firststate, and to axially move the reciprocating valve downstream in thesecond state.
 5. The apparatus according to claim 4, wherein the valvedriver comprises a rod (a) disposed parallel to a longitudinal axis ofpump portion 124, and (b) configured to move the reciprocating valveupstream in the first state and downstream in the second state.
 6. Theapparatus according to claim 5, wherein the rod is (a) disposeddownstream of the reciprocating valve, and (b) configured to push thereciprocating valve upstream in the first state, and to pull thereciprocating valve downstream in the second state.
 7. The apparatusaccording to claim 1, wherein the apparatus does not comprise anyleaflets for allowing and inhibiting blood flow in the blood vessel inaddition to the set of one or more leaflets of the reciprocating valve.8. The apparatus according to claim 1, wherein the apparatus does notcomprise any leaflets that are configured to (a) open when the set ofone or more leaflets of the reciprocating valve are in the closedconfiguration and (b) close when the set of one or more leaflets of thereciprocating valve are in the open configuration.
 9. The apparatusaccording to claim 1, wherein the reciprocating valve comprises acylindrical housing to which the set of one or more leaflets is coupledsuch that the leaflets in the second state inhibit the blood flowthrough the cylindrical housing, and wherein the valve driver isconfigured to drive the cylindrical housing to move axially with respectto the anchor in the reciprocating pattern.
 10. The apparatus accordingto claim 9, wherein the anchor comprises a generally cylindrical stent,and wherein the pump portion further comprises a blood-proof membranethat is fixed to the stent and to the cylindrical housing so as to (a)inhibit blood flow between the cylindrical housing and the stent and (b)allow axial movement of the cylindrical housing with respect to thestent.
 11. The apparatus according to claim 10, wherein the blood-proofmembrane is fixed to an external surface of the cylindrical housing. 12.The apparatus according to claim 11, wherein the valve driver isconfigured to axially move the cylindrical housing upstream in the firststate, and to axially move the cylindrical housing downstream in thesecond state, and wherein the blood-proof membrane is fixed to adownstream portion of the external surface of the cylindrical housingand is not fixed to an upstream portion of the external surface of thecylindrical housing, the upstream portion having an axial length,measured along a central longitudinal axis of the cylindrical housing,of at least 5 mm.
 13. The apparatus according to claim 10, wherein theblood-proof membrane, the cylindrical housing, and the stent arearranged such that a degree of invagination of the blood-proof membranechanges during axial movement of the cylindrical housing with respect tothe anchor.
 14. The apparatus according to claim 13, wherein the valvedriver is configured to axially move the cylindrical housing upstream inthe first state, and to axially move the cylindrical housing downstreamin the second state, and wherein the blood-proof membrane, thecylindrical housing, and the stent are arranged such that the degree ofinvagination of the blood-proof membrane increases during downstreammovement of the cylindrical housing and decreases during upstreammovement of the cylindrical housing.
 15. The apparatus according toclaim 13, wherein the valve driver is configured to axially move thecylindrical housing upstream in the first state, and to axially move thecylindrical housing downstream in the second state, wherein theblood-proof membrane, the cylindrical housing, and the stent arearranged such that the blood-proof membrane is shaped so as to define anannular chamber between at least a portion of an external surface of thecylindrical housing and at least a portion of an inner surface of thegenerally cylindrical stent, and wherein the annular chamber has an opendownstream end and a closed upstream end defined by a curved portion ofthe blood-proof membrane.
 16. The apparatus according to claim 9,wherein the valve driver is configured to axially move the cylindricalhousing upstream in the first state, and to axially move the cylindricalhousing downstream in the second state, and wherein the valve driver isconfigured to drive the cylindrical housing to move axially between 10and 20 mm in each of an upstream direction and a downstream directionduring an entire cycle of the reciprocating pattern.
 17. The apparatusaccording to claim 9, wherein the valve driver is configured to axiallymove the cylindrical housing downstream in the second state, such thatthe reciprocating valve pushes blood at a rate of between 10 and 20 ccper second.
 18. The apparatus according to claim 9, wherein the valvedriver is configured to axially move the cylindrical housing downstreamin the second state, such that the reciprocating valve pushes between 10and 20 cc during an entire operating cycle of the reciprocating pattern.19. The apparatus according to claim 1, wherein the valve driver isconfigured to drive the reciprocating valve in the reciprocating patternat a frequency of 2-5 Hz.
 20. The apparatus according to claim 1,wherein the apparatus is not configured to coordinate the reciprocatingpattern with a cardiac cycle of the subject.
 21. The apparatus accordingto claim 1, wherein the apparatus does not comprise any sensor of heartrate or cardiac cycle.
 22. A method comprising: deploying in a lumen ofa blood vessel of a subject, in a location that is downstream of anative aortic valve of a heart of the subject, a reciprocating valvecomprising a set of one or more leaflets; and activating a valve driverto drive the reciprocating valve in a reciprocating pattern between: (i)a first state in which the leaflets are in an open configurationallowing blood flow through the reciprocating valve, and (ii) a secondstate in which the leaflets are in a closed configuration inhibitingblood flow through the reciprocating valve.